Lee's mother is 5 times as old as him. His mother will be 42 years old in 7 years' time. In how many years' time will Lee's age be 60% that of his mother's?
| |
Lee's mother |
Lee |
Difference |
Before
(now) |
5x1 =
5 u |
1x1 =
1 u |
4x1 =
4 u |
| Change 1 |
+ 7 |
+ 7 |
|
| After 1 |
42 |
|
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x2 =
10 u |
3x2 =
6 u |
2x2 =
4 u |
60% =
60100 =
35 Lee's mother : Lee = 5 : 3
The difference in age between Lee's mother and Lee always remains the same. Make the difference in age between Lee's mother and Lee the same. LCM of 4 and 2 is 4.
5 u + 7 = 42
5 u = 42 - 7
5 u = 35
1 u = 35 ÷ 5 = 7
Number of years' time when Lee's age will be 60% that of his mother's
= 10 u - 42
= 10 x 7 - 42
= 70 - 42
= 28
Answer(s): 28
